The present invention generally relates to a method and apparatus for controlling a device connection, and, more particularly, to a method and apparatus for controlling the connecting of devices to a network or host device, such as a personal computer.
When connecting a peripheral device to a host device or a network, such as connecting a digital video camera to a personal computer, the peripheral device is usually connected to the host device while the host device power is turned off. This is because a personal computer does not recognize a device if the device is connected to the computer after the power has been turned on.
It is desirable to be able to connect a device to a network or host device while the network or host device is powered on. This is called hot plug-in or hot swapping. It is also desirable that the peripheral device and the host device be able to communicate without encountering any device conflicts. A device conflict occurs when more than one device attempts to use the same device address. A standard, known as plug-and-play, allows compliant peripheral devices to be connected to a host and the host detects connected devices and assigns an address or identifier to each peripheral device to avoid device conflicts.
The key issue for hot plug-in and plug-and-play is always to recognize whether the device has been connected to the network. Generally, the device has a cable connection controller (connection device) for connecting to the network. The device can also be connected to the network through an external connection device. The connection device outputs a status signal indicating the presence of the device to a connection terminal of the network. The status signal has a predetermined bias voltage.
All of the devices connectable to the network are constructed to output the status signal. Plural devices connected to the network mutually detect the status signal output from a remote device so that the network may be reconstructed. Thus, the device recognizes whether the remote device is connected to the network by detecting the remote status signal. This recognition of the remote device enables data to be transferred between the devices or between the device and the personal computer.
However, the devices always outputs the status signal even when in the connected state. In other words, the device outputs the status signal even when there is no need to connect to the network. Hence, a circuit that outputs the status signal operates at any time, which increases the power consumption of the device.
It is an object of the present invention to provide a device connection control apparatus and method that reduce the power consumption.
In one aspect of the present invention, a connection control apparatus is provided that controls a connection between a local node and a remote node by sending and receiving a status signal therebetween. The apparatus includes a status generation circuit generating a local status signal and a status detection circuit for receiving a remote status signal generated at the remote node and for detecting a state of the received remote status signal. A status control circuit is connected to the status generation circuit and the status detection circuit and selectively controls the status generation circuit. The status control circuit disables the status generation circuit when the detected state of the remote status signal denotes deactivation and enables the status generation circuit when either the local node starts sending and receiving data with the remote node or the detected state of the remote status signal denotes activation.
In another aspect of the present invention, a method is provided that controls a connection between a local node and a remote node by sending and receiving a status signal therebetween. The local node and the remote node each is connected to a connection control apparatus. Each connection apparatus includes a status generation circuit for generating a local status signal and a status detection circuit for detecting a remote status signal generated by the status generation circuit of the connection controller of the remote node. First, the status generation circuit is disabled when deactivation of the remote status signal is detected by the status detection circuit. Then, the status generation circuit is enabled when the local node starts sending and receiving data with the remote node or when activation of the remote status signal is detected.
In yet another aspect of the present invention, a connection device is provided that connects an electronic device to a remote device via a network. The connection device includes a net interface circuit connected to a network for transmitting a local status signal over the network and for receiving a remote status signal transmitted over the network. A local status generation circuit is connected to the net interface circuit. The local status generation circuit generating the local status signal in response to a control signal. A remote status detection circuit is connected to the net interface circuit. The remote status detection circuit detects a remote status signal received by the net interface circuit. In response to detecting the remote status signal, the remote status detection circuit activates a detection signal. A host interface circuit is connected to the electronic device, passes data to the electronic device, and receives data from the electronic device. A data transfer circuit is connected between the host interface circuit and the net interface circuit, passes data therebetween, and generates a data transfer control signal indicating that data is to be transferred between the remote device and the electronic device. A status control circuit is connected to the local status generation circuit for providing the control signal thereto, connected to the remote status detection circuit for receiving the remote status signal, and connected to the data transfer circuit for receiving a data transfer control signal therefrom. The status control circuit activates the control signal in response to the data transfer control signal or the detection signal.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.